immunoelectrophoresis im·mu·no·e·lec·tro·pho·re·sis (ĭm'yə-nō-ĭ-lěk'trə-fə-rē'sĭs, ĭ-myōō'-)n. The separation and identification of proteins based on differences in their electrophoretic mobility through agar or a similar medium and in their reactivity with antibodies.